Sealing material of polypropylene with improved optical performance

ABSTRACT

Polypropylene composition comprising a propylene homopolymer having a melt flow rate MFR 2  (230° C.) in the range of 1.0 to 20.0 g/10 min and a propylene copolymer, said copolmyer comprisesa polypropylene fraction having a comonomer content of not more than 1.0 wt.-%, the comomers are C 5  to C 12  α-olefins, anda propylene copolymer fraction having a comonomer content 4.0 to 20.0 wt.-%, the comomers are C 5  to C 12  α-olefins, wherein furtherthe propylene copolymer has a comonomer content of at least 2.5 wt.-%, the comomers are C 5  to C 12  α-olefins, the melt flow rate MFR 2  (230° C.) of the propylene homopolymer is higher than the melt flow rate MFR 2  (230° C.) of the polypropylene fraction, the weight ratio of the polypropylene fraction to the propylene copolymer fraction is in the range of 30/70 to 70/30, andthe weight ratio of the propylene copolymer to the propylene homopolymer is in the range of 95/5 to 75/25.

The present invention is directed to a new propylene copolymercomposition, its manufacture and use.

Polypropylenes are suitable for many applications. For instancepolypropylene is applicable in areas where sealing properties play animportant role, like in the food packing industry. Irrespectively fromthe polymer type, a polymer must fulfill at best all desired endproperties and additionally must be easily processable, i.e. mustwithstand stress. However end properties and processing properties actoften in a conflicting manner.

In many cases, the seal which is formed between the surfaces to besealed is put under load while it is still warm. This means that thehot-tack properties of the polypropylene are crucial to ensure a strongseal is formed even before cooling. But not only the hot tack strengthshould be rather high but also the heat sealing initiation temperatureshould be rather low. By operating at lower temperature there is thebenefit that the article to be sealed is not exposed to hightemperature. There are also economic advantages since lower temperaturesare of course cheaper to generate and maintain.

Apart from the sealing properties high melting temperatures are requiredto avoid stickiness problems during the manufacture of biaxiallyoriented films. Further in some applications good optical properties aredesired.

Accordingly the object of the present invention is to provide apolypropylene composition with high hot tack strength, low heat sealinginitiation temperature (SIT), good optical properties and which enablesto produce biaxially oriented films with high processing speeds.

The finding of the present invention is to provide a polypropylenecomposition comprising a propylene homopolymer and a propylene copolymerwith rather high comonomer content, the comonomers are long chainα-olefins, and said propylene copolymer comprises two differentfractions, said fractions differ in the comonomer content.

Accordingly in a first aspect the present invention is directed to apolypropylene composition comprising

-   (a) a propylene homopolymer (H-PP) having a melt flow rate MFR₂    (230° C.) measured according to ISO 1133 in the range of 1.0 to 20.0    g/10 min, and-   (b) a propylene copolymer (C-PP) comprising    -   (b-1) a polypropylene fraction (A) having a comonomer content of        not more than 1.0 wt.-%, the comomers are C₅ to C₁₂ α-olefins,        and    -   (b-2) a propylene copolymer fraction (B) having a comonomer        content 4.0 to 20.0 wt.-%, the comomers are C₅ to C₁₂ α-olefins,-   wherein further-   (c) the propylene copolymer (C-PP) has a comonomer content of at    least 2.0 wt.-%, preferably of at least 2.5 wt.-%, the comomers are    C₅ to C₁₂ α-olefins,-   (d) the melt flow rate MFR₂ (230° C.) measured according to ISO 1133    of the propylene homopolymer (H-PP) is higher than the melt flow    rate MFR₂ (230° C.) measured according to ISO 1133 of the    polypropylene fraction (A),-   (e) the weight ratio [(A)/(B)] of the polypropylene fraction (A) to    the propylene copolymer fraction (B) is in the range of 30/70 to    70/30, and-   (f) the weight ratio [(C-PP)/(H-PP)] of the propylene copolymer    (C-PP) to the propylene homopolymer(H-PP) is in the range of 95/5 to    75/25.

Preferably the propylene homopolymer (H-PP) according to the firstaspect of the present invention has <2,1> regiodefects of equal or morethan 0.4 mol.-% determined by ¹³C-spectroscopy or the propylenehomopolymer (H-PP) has <2,1> regiodefects of less than 0.4 mol.-%determined by ¹³C-spectroscopy, the latter being preferred.

In a second aspect, the present invention is directed to a polypropylenecomposition comprising

-   (a) a propylene homopolymer (H-PP) having <2,1> regiodefects of less    than 0.4 mol.-% determined by ¹³C-spectroscopy, and-   (b) a propylene copolymer (C-PP) comprising    -   (b-1) a polypropylene fraction (A) having a comonomer content of        not more than 1.0 wt.-%, the comomers are C₅ to C₁₂ α-olefins,        and    -   (b-2) a propylene copolymer fraction (B) having a comonomer        content 4.0 to 20.0 wt.-%, the comomers are C₅ to C₁₂ α-olefins,-   wherein further-   (c) the propylene copolymer (C-PP) has a comonomer content of at    least 2.0 wt.-%, preferably of at least 2.5 wt.-%, the comomers are    C₅ to C₁₂ α-olefins,-   (d) the weight ratio [(A)/(B)] of the polypropylene fraction (A) to    the propylene copolymer fraction (B) is in the range of 30/70 to    70/30, and-   (e) the weight ratio [(C-PP)/(H-PP)] of the propylene copolymer    (C-PP) to the propylene homopolymer(H-PP) is in the range of 95/5 to    75/25.

According to the second aspect it is especially preferred that

-   (a) the propylene homopolymer (H-PP) has a melt flow rate MFR₂ (230°    C.) measured according to ISO 1133 in the range of 1.0 to 20.0 g/10    min,-   and/or-   (b) the melt flow rate MFR₂ (230° C.) measured according to ISO 1133    of the propylene homopolymer (H-PP) is higher than the melt flow    rate MFR₂ (230° C.) measured according to ISO 1133 of the    polypropylene fraction (A).

It has surprisingly been found that polypropylene compositions accordingto the first and second aspect have a high melting temperature Tm, a lowheat sealing initiation temperature (SIT) and good optical properties(see example section).

In the following the invention according to the first and second aspectare defined in more detail together.

Preferably the polypropylene composition comprises the propylenehomopolymer (H-PP) and the propylene copolymer (C-PP) as the onlypolymer components. Further it is appreciated that the propylenecopolymer (C-PP) comprises the propylene copolymer faction (A) and thepropylene copolymer fraction (B) as the only polymer components.

As stated above it is preferred that the propylene homopolymer(H-PP) andpropylene copolymer (C-PP) are the only polymer components of thepolypropylene composition. Accordingly the amount of the propylenehomopolymer(H-PP) and propylene copolymer (C-PP) together within thepolypropylene composition is at least 80 wt.-%, more preferably at least90 wt.-%, yet more preferably at least 95 wt.-%, like at least 98 wt.-%.The remaining part are typical additives, like antioxidants, nucleatingagents, slip agents and/or antistatic agents. Further it is appreciatedthat the propylene homopolymer(H-PP) and propylene copolymer (C-PP) arepresent in the polypropylene composition of the instant invention in aspecific weight ratio. Thus in a preferred embodiment the weight ratio[(C-PP)/(H-PP)] of the propylene copolymer (C-PP) to the propylenehomopolymer(H-PP) is in the range of 95/5 to 75/25, more preferably inthe range of 90/10 to 80/20, yet more preferably in the range of 88/12to 83/17.

Further, it is preferred that the polypropylene composition of thepresent invention has a melt flow rate (MFR) given in a specific range.The melt flow rate measured under a load of 2.16 kg at 230° C. (ISO1133) is denoted as MFR₂ (230° C.). Accordingly, it is preferred that inthe present invention the polypropylene composition has a the melt flowrate MFR₂ (230° C.) measured according to ISO 1133 in the range of 1.0to 50.0 g/10 min, more preferably in the range of 2.0 to 20.0 g/10 min,still more preferably in the range of 4.0 to 12.0 g/10 min.

The polypropylene composition according to this invention can be furtherdefined by its comonomer content. A “comonomer” according to thisinvention is a polymerizable unit different to propylene. Accordinglythe polypropylene composition according to this invention shall have acomonomer content in the range of 1.0 to 10.0 wt.-%, more preferably inthe range of 2.0 to 8.0 wt.-%, still more preferably in the range of 3.0to 7.0 wt.-%.

As stated above the polypropylene composition comprises as main polymercomponents the propylene homopolymer (H-PP) and the propylene copolymer(C-PP). Accordingly the comonomers originate from the propylenecopolymer (C-PP). Thus the comonomers identified for the polypropylenecomposition are preferably the comonomers of the propylene copolymer(C-PP). Therefore concerning the preferred comonomers of thepolypropylene composition it is referred to the preferred comonomers ofthe propylene copolymer (C-PP) as defined below.

As mentioned above, the inventive polypropylene composition shall beespecially suitable for the packing industry. Accordingly good sealingproperties are desired, like rather low heat sealing initiationtemperature (SIT). Further the processing speed in the process ofbiaxially oriented polypropylene can be raised in case the used polymeris featured by rather high melting temperature.

Accordingly it is preferred that the polypropylene composition fulfillsthe equation (I), more preferably the equation (Ia), still morepreferably the equation (Ib),

Tm−SIT≧24° C.  (I),

Tm−SIT≧30° C.  (Ia),

Tm−SIT≧39° C.  (Ib),

wherein

-   Tm is the melting temperature given in centigrade [° C.] of the    polypropylene composition,-   SIT is the heat sealing initiation temperature (SIT) given in    centigrade [° C.] of the polypropylene composition.

The melting temperature (T_(m)) measured according to ISO 11357-3 of thepolypropylene composition is preferably at least 140.0° C., morepreferably of at least 145° C., yet more preferably of at least 148° C.,like at least 150° C. Thus it is in particular appreciated that themelting temperature (T_(m)) measured according to ISO 11357-3 of thecomposition is in the range of 140 to 160° C., more preferably in therange of 145 to 160° C., yet more preferably in the range of 148 to 158°C. The melting temperatures of above 150° C. are especially achievablewith a polypropylene homopolymer produced in the presence of aZiegler-Natta catalyst, i.e. with a polypropylene having <2,1>regiodefects of less than 0.4 mol.-% determined by ¹³C-spectroscopy.

Additionally it is appreciated that the polypropylene composition of theinstant invention has crystallization temperature (T_(c)) measuredaccording to ISO 11357-3 of at least 100° C., more preferably of atleast 102° C. Accordingly the polypropylene composition has preferably acrystallization temperature (T_(c)) measured according to ISO 11357-3 inthe range of 100 to 112° C., more preferably in the range of 102 to 112°C.

Furthermore it is preferred that the polypropylene composition has aheat sealing initiation temperature (SIT) of not more than 120° C., morepreferably not more than 110° C., still more preferably in the range of100 to 120° C., yet more preferably in the range of 102 to 118° C.

Additionally the propylene copolymer can be defined by the xylene coldsoluble (XCS) content measured according to ISO 6427. Accordingly thepolypropylene composition is preferably featured by a xylene coldsoluble (XCS) content of below 18.0 wt.-%, more preferably of below 15.0wt.-%, yet more preferably equal or below 10.0 wt.-%, still morepreferably below 5.0 wt.-%, like below 4.0 wt.-%. Thus it is inparticular appreciated that the polypropylene composition of the instantinvention has a xylene cold soluble (XCS) content in the range of 0.3 to18.0 wt.-%, more preferably in the range of 0.5 to 10.0 wt.-%, yet morepreferably in the range of 0.5 to 5.0 wt.-%.

In the following the polypropylene composition is defined further by itsindividual components, i.e. by the propylene homopolymer (H-PP) and bythe propylene copolymer (C-PP).

The expression propylene homopolymer used in the instant inventionrelates to a polypropylene that consists substantially, i.e. of morethan 99.7 wt.-%, still more preferably of at least 99.8 wt.-%, ofpropylene units. In a preferred embodiment only propylene units in thepropylene homopolymer are detectable. The comonomer content can bedetermined with ¹³C NMR spectroscopy, as described below in theexamples.

The propylene homopolymer (H-PP) has preferably a melt flow rate MFR₂(230° C.) measured according to ISO 1133 in the range of 1.0 to 20.0g/10 min, more preferably in the range of 2.0 to 15.0 g/10 min. It isadditionally preferred that the propylene homopolymer (H-PP) has highermelt flow rate MFR₂ (230° C.) measured according to ISO 1133 than thepolypropylene fraction (A) of the propylene copolymer (C-PP).

The propylene homopolymer (H-PP) of the present invention can be eitherobtained by a process in which a single site catalyst has been used or aZiegler-Natta catalyst. Typically the polypropylenes obtained by thesetwo catalyst type differ in their <2,1> regiodefects. Accordingly it isappreciated that the propylene homopolymer has

-   (a)<2,1> regiodefects determined by ¹³C-spectroscopy of equal or    more than 0.4 mol.-%, more preferably of equal or more than 0.6    mol.-%, like in the range of 0.7 to 0.9 mol.-%,-   or-   (b)<2,1> regiodefects determined by ¹³C-spectroscopy of less than    0.4 mol.-%, more preferably of equal or less than 0.2 mol.-%, like    of equal or less than 0.1 mol.-%.

In one embodiment the propylene homopolymer (H-PP) has <2,1>regiodefects as defined under item (b) of the previous paragraph.

Further it is appreciated that the xylene soluble content (XCS) of thepropylene homopolymer (H-PP) is rather low. Thus it is preferred thatthe xylene soluble content (XCS) according to ISO 6427 of the propylenehomopolymer (H-PP) is below 3.0 wt.-%, more preferably below 2.0 wt.-%.In case the propylene homopolymer (H-PP) has <2,1> regiodefects of equalor more than 0.4 mol.-% the xylene soluble content (XCS) according toISO 6427 is below 1.5 wt.-%, like in the range of 0.5 to 1.2 wt.-%.

The melting temperature Tm of the propylene homopolymer (H-PP) ispreferably at least 145° C., more preferably at least 148° C. In casethe propylene homopolymer (H-PP) has <2,1> regiodefects of less than 0.4mol.-%, the melting temperature is preferably at least 150° C., like atleast 152° C.

The propylene copolymer (C-PP) according to this invention is featuredby a rather high comonomer content. Accordingly the propylene copolymer(C-PP) according to this invention shall have a comonomer content of atleast 2.0 wt.-%, more preferably of at least 2.5 wt.-%, still morepreferably of at least 2.8 wt.-%, yet more preferably of at least 3.0wt.-%. However the propylene copolymer (C-PP) according to thisinvention shall not comprise an elastomeric component. Thus it ispreferred that the propylene copolymer (C-PP) according to thisinvention has a comonomer content in the range of 2.0 to 15.0, like 2.5to 15.0 wt.-%, more preferably in the range of 2.5 to 12.0 wt.-%, stillmore preferably in the range of 2.8 to 10.0 wt.-%, like in the range of3.0 to 10.0 wt.-%.

The comonomers of the propylene copolymer (C-PP) are C₅ to C₁₂α-olefins, e.g. 1-hexene and/or 1-octene. The propylene copolymer (C-PP)may contain more than one type of comonomer. Thus the propylenecopolymer (C-PP) may contain one, two or three different comonomers, thecomonomers are selected from the group of C₅ α-olefin, C₆ α-olefin, C₇α-olefin, C₈ α-olefin, C₉ α-olefin, C₁₀ α-olefin, C₁₁ α-olefin, and C₁₂α-olefin. However it is preferred that the propylene copolymer (C-PP)contains only one type of comonomer. Preferably the propylene copolymer(C-PP) comprises—apart from propylene—only 1-hexene and/or 1-octene. Inan especially preferred embodiment the comonomer of the propylenecopolymer (C-PP) is only 1-hexene.

The propylene copolymer (C-PP) as well as the propylene copolymerfraction (C-A) and the propylene copolymer fraction (B) as defined indetail below are preferably random propylene copolymers. The term“random copolymer” has to be preferably understood according to IUPAC(Pure Appl. Chem., Vol. No. 68, 8, pp. 1591 to 1595, 1996). Preferablythe molar concentration of comonomer dyads, like 1-hexene dyads, obeysthe relationship

[HH]<[H] ²

wherein[HH] is the molar fraction of adjacent comonomer units, like of adjacent1-hexene units, and[H] is the molar fraction of total comonomer units, like of total1-hexene units, in the polymer.

Preferably the propylene copolymer (C-PP) as well as the polypropylenefraction (A) and the propylene copolymer fraction (B) as defined indetail below are isotactic. Accordingly it is appreciated that thepropylene copolymer (C-PP), the propylene copolymer fraction (A) and thepropylene copolymer fraction (B) have a rather high isotactic triadconcentration, i.e. higher than 90%, more preferably higher than 92%,still more preferably higher than 93% and yet more preferably higherthan 95%, like higher than 97%.

The propylene copolymer (C-PP) can be further defined by its crystallinefractions determined by the stepwise isothermal segregation technique(SIST). The stepwise isothermal segregation technique (SIST) provides apossibility to determine the lamella thickness distribution. The precisemeasuring method is specified in the example section. Thereby ratherhigh amounts of polymer fractions crystallizing at high temperaturesindicate a rather high amount of thick lamellae. Thus it is appreciatedthat the propylene copolymer (C-PP) comprises at least 20.0 wt-%, morepreferably at least 25.0 wt.-%, yet more preferably at least 28.0 wt.-%,still yet more preferably at least 30.0 wt.-%, like at least 33.0 wt.-%,of a crystalline fraction having a lamella thickness of at least 5.7 nm,preferably of 5.7 to 7.4 nm, wherein said fraction is determined by thestepwise isothermal segregation technique (SIST). Accordingly in apreferred embodiment the propylene copolymer (C-PP) comprises 20.0 to45.0 wt.-%, more preferably 25.0 to 40 wt.-%, like 28.0 to 37.0 wt.-%,of a crystalline fraction having a lamella thickness of at least 5.7 nm,preferably of 5.7 to 7.4 nm. Additionally it is appreciated that thepropylene copolymer (C-PP) comprises a considerable amount of polymerfractions crystallizing at low temperatures. Thus it is preferred thatthe propylene copolymer (C-PP) comprises at least 10.0 wt-%, morepreferably at least 12.0 wt.-%, yet more preferably 10.0 to 20.0 wt.-%,still yet more preferably 12.0 to 18.0 wt.-%, of a crystalline fractionhaving a lamella thickness of below 3.0 nm, preferably of 2.0 to below3.0 nm, wherein said fraction is determined by the stepwise isothermalsegregation technique (SIST). In an especially preferred embodiment thepropylene copolymer (C-PP) comprises

-   (a) 20.0 to 45.0 wt.-%, preferably 25.0 to 40.0 wt.-%, more    preferably 28.0 to 37.0 wt.-%, of a crystalline fraction having a    lamella thickness of at least 5.7 nm, preferably of 5.7 to 7.4 nm,    and-   (b1) 20.0 to 36.0 wt.-%, preferably 23.0 to 34.0 wt.-%, more    preferably 24.0 to 32.0 wt.-%, of a crystalline fraction having a    lamella thickness of 4.7 to below 5.7 nm, and/or-   (b2) 10.0 to 20.0 wt.-%, preferably 12.0 to 18.0 wt.-%, more    preferably 13.0 to 17.0 wt.-%, of a crystalline fraction having a    lamella thickness of below 3.0 nm, preferably of 2.0 to below 3.0    nm.

The molecular weight distribution (MWD) is the relation between thenumbers of molecules in a polymer and the individual chain length. Themolecular weight distribution (MWD) is expressed as the ratio of weightaverage molecular weight (M_(w)) and number average molecular weight(M_(n)). The number average molecular weight (M_(n)) is an averagemolecular weight of a polymer expressed as the first moment of a plot ofthe number of molecules in each molecular weight range against themolecular weight. In effect, this is the total molecular weight of allmolecules divided by the number of molecules. In turn, the weightaverage molecular weight (M_(w)) is the first moment of a plot of theweight of polymer in each molecular weight range against molecularweight.

The number average molecular weight (M_(n)) and the weight averagemolecular weight (M_(w)) as well as the molecular weight distribution(MWD) are determined by size exclusion chromatography (SEC) using WatersAlliance GPCV 2000 instrument with online viscometer. The oventemperature is 140° C. Trichlorobenzene is used as a solvent (ISO16014).

Accordingly it is preferred that the propylene copolymer (C-PP) has aweight average molecular weight (M_(w)) from 100 to 700 kg/mol, morepreferably from 150 to 400 kg/mol.

The number average molecular weight (M.) of the propylene copolymer(C-PP) is preferably in the range of 20 to 200 kg/mol, more preferablyfrom 30 to 150 kg/mol.

Further it is appreciated that the molecular weight distribution (MWD)measured according to ISO 16014 is not more than 4.5, more preferablynot more than 4.0, like not more than 3.5. Thus the molecular weightdistribution (MWD) of the propylene copolymer (C-PP) is preferablybetween 1.5 to 4.5, still more preferably in the range of 1.5 to 4.0,like 2.0 to 3.5.

Furthermore, it is preferred that the propylene copolymer (C-PP) of thepresent invention has a melt flow rate (MFR) given in a specific range.The melt flow rate measured under a load of 2.16 kg at 230° C. (ISO1133) is denoted as MFR₂ (230° C.). Accordingly, it is preferred thatthe propylene copolymer (C-PP) has a the melt flow rate MFR₂ (230° C.)measured according to ISO 1133 of at least 2.0 g/10 min, more preferablyof at least 4.0 g/10 min, still more preferably in the range of 2.0 to50.0 g/10 min, yet more preferably in the range of 4.0 to 30.0 g/10 min,like in the range of 5.0 to 25.0 g/10 min.

The melting temperature (T_(m)) measured according to ISO 11357-3 of thepropylene copolymer (C-PP) is rather high, i.e. of at least 140.0° C.,more preferably of at least 145° C. Thus it is in particular appreciatedthat the melting temperature (T_(m)) measured according to ISO 11357-3of the propylene copolymer (C-PP) is in the range of 140 to 160° C.,more preferably in the range of 145 to 155° C.

The xylene cold soluble fraction (XCS) measured according to ISO 6427contains polymer chains of low stereoregularity and is an indication forthe amount of non-crystalline areas. Accordingly propylene copolymer(C-PP) is preferably featured by rather low xylene cold soluble (XCS)content of below 3.5 wt.-%, more preferably of below 3.3 wt.-%, yet morepreferably equal or below 3.0 wt.-%, still more preferably below 2.0wt.-%, like below 1.5 wt.-%. Thus it is in particular appreciated thatthe propylene copolymer (C-PP) of the instant invention has a xylenecold soluble (XCS) content in the range of 0.3 to 3.5 wt.-%, morepreferably in the range of 0.5 to 3.3 wt.-%, yet more preferably in therange of 0.5 to 1.5 wt.-%.

The propylene copolymer (C-PP) is further defined by its polymerfractions present. Accordingly the propylene copolymer (C-PP) of thepresent invention comprises at least, preferably consists of, twofractions, namely the polypropylene fraction (A) and the propylenecopolymer fraction (B). The polypropylene fraction (A) is preferably thehigh molecular weight fraction whereas the propylene copolymer fraction(B) is the low molecular weight fraction. Accordingly the ratio MFR(A)/MFR(C-PP) is below 1.0, more preferably below 0.50, yet morepreferably below 0.30, still more preferably below 0.25 wherein

-   MFR (A) is the melt flow rate MFR₂ (230° C.) [g/10 min] measured    according to ISO 1133 of the polypropylene fraction (A),-   MFR(C-PP) is the melt flow rate MFR₂ (230° C.) [g/10 min] measured    according to ISO 1133 of the propylene copolymer (C-PP), and

Further it is appreciated that the polypropylene fraction (A) has a meltflow rate MFR₂ (230° C.) measured according to ISO 1133 of not more than5.0 g/10 min, more preferably of not more than 3.0 g/10 min, still morepreferably of not more than 2.0 g/10 min, yet more preferably in therange of 0.01 to 5.0 g/10 min, like 0.1 to 3.0 g/10 min.

As a low melt flow rate indicates a high molecular weight, it ispreferred that the polypropylene (A) has a weight average molecularweight (M_(w)) of at least 350 kg/mol, more preferably of at least 400kg/mol, still more preferably of at least 500 kg/mol, yet morepreferably in the range of 350 to 1,000 kg/mol, like in the range of 400to 600 kg/mol.

On the other hand the propylene copolymer fraction (B) shall have a(significantly) higher melt flow rate than the polypropylene fraction(A). Accordingly it is preferred that the propylene copolymer fraction(B) has a melt flow rate MFR₂ (230° C.) measured according to ISO 1133of more than 10.0 g/10 min, more preferably of more than 15.0 g/10 min,still more preferably of more than 20.0 g/10 min, yet more preferably inthe range of more than 10.0 to 200.0 g/10 min, like 20.0 to 100.0 g/10min.

Accordingly it is appreciated that the propylene copolymer fraction (B)has a weight average molecular weight (M_(w)) of below 250 kg/mol, stillmore preferably of below 200 kg/mol, yet more preferably below 180kg/mol, like in the range of 100 to 200 kg/mol.

To achieve such a melt flow rate MFR₂ (230° C.) of the propylenecopolymer (C-PP) it is preferred that the weight ratio of thepolypropylene fraction (A) and the propylene copolymer fraction (B) isin a specific range. Accordingly weight ratio of the polypropylenefraction (A) to the propylene copolymer fraction (B) is preferably inthe range of 30/70 to 70/30, more preferably 40/60 to 45/55.

As stated above, in a preferred embodiment the propylene copolymer(C-PP) comprises, preferably consists of, two fractions, namely thepolypropylene fraction (A) and the propylene copolymer fraction (B).Further the polypropylene fraction (A) is preferably the comonomer leanfraction whereas the propylene copolymer fraction (B) is the comonomerrich fraction.

Thus it is appreciated that the polypropylene fraction (A) has acomonomer content of not more than 1.0 wt.-%. Accordingly thepolypropylene fraction (A) can be a propylene copolymer fraction (C-A)or a propylene homopolymer fraction (H-A), the latter being preferred.

In case the polypropylene fraction (A) is a propylene copolymer fraction(C-A) the comonomer content is in the range of 0.2 to 1.0 wt.-%,preferably in the range 0.5 to 1.0 wt.-%. More preferably the propylenecopolymer fraction (C-A) is a random propylene copolymer. The comonomersof the propylene copolymer fraction (C-A) are C₅ to C₁₂ α-olefins, morepreferably the comonomers of the propylene copolymer fraction (C-A) areselected from the group of C₅ α-olefin, C₆ α-olefin, C₇ α-olefin, C₈α-olefin, C₉ α-olefin, C₁₀ α-olefin, C₁₁ α-olefin, an C₁₂ α-olefin,still more preferably the comonomers of the propylene copolymer fraction(C-A) are 1-hexene and/or 1-octene. The propylene copolymer fraction(C-A) may contain more than one type of comonomer. Thus the propylenecopolymer fraction (C-A) of the present invention may contain one, twoor three different comonomers. However it is preferred that thepropylene copolymer fraction (C-A) contains only one type of comonomer.Preferably the propylene copolymer fraction (C-A) comprises—apart frompropylene—only 1-hexene and/or 1-octene. In an especially preferredembodiment the comonomer of the propylene copolymer fraction (C-A) isonly 1-hexene.

Thus the propylene copolymer fraction (C-A) is in one preferredembodiment a propylene copolymer of propylene and 1-hexene only, whereinthe 1-hexene content is in the range of 0.2 to 1.0 wt-%, preferably inthe range of 0.5 to 1.0 wt-%.

The propylene copolymer fraction (B) has preferably a higher comonomercontent than the polypropylene fraction (A). Accordingly the propylenecopolymer fraction (B) has a comonomer content of 4.0 wt.-% to 20.0wt.-%, preferably of 4.0 to 10.0 wt.-%.

More preferably the propylene copolymer fraction (B) is a randompropylene copolymer.

The comonomers of the propylene copolymer fraction (B) are C₅ to C₁₂α-olefins, more preferably the comonomers of the propylene copolymerfraction (B) are selected from the group of C₅ α-olefin, C₆ α-olefin, C₇α-olefin, C₈ α-olefin, C₉ α-olefin, C₁₀ α-olefin, C₁₁ α-olefin, an C₁₂α-olefin, still more preferably the comonomers of the propylenecopolymer fraction (B) are 1-hexene and/or 1-octene. The propylenecopolymer fraction (B) may contain more than one type of comonomer. Thusthe propylene copolymer fraction (B) of the present invention maycontain one, two or three different comonomers. However it is preferredthat the propylene copolymer fraction (B) contains only one type ofcomonomer. Preferably the propylene copolymer fraction (B)comprises—apart from propylene—only 1-hexene and/or 1-octene. In anespecially preferred embodiment the comonomer of the propylene copolymerfraction (B) is only 1-hexene.

Thus the propylene copolymer fraction (B) is in a preferred embodiment apropylene copolymer of propylene and 1-hexene only, wherein the 1-hexenecontent is in the range of 4.0 to 10.0 wt.-%.

It is in particular preferred that the comonomers of the propylenecopolymer fraction (C-A) and of the propylene copolymer fraction (B) arethe same. Accordingly in one preferred embodiment the propylenecopolymer c (C-PP) of the instant invention comprises, preferablycomprises only, a propylene copolymer fraction (C-A) and a propylenecopolymer fraction (B), in both polymers the comonomer is only 1-hexene.

In an especially preferred embodiment the propylene copolymer (C-PP) ofthe instant invention comprises, preferably comprises only, a propylenehomopolymer fraction (H-A) and a propylene copolymer fraction (B),wherein the comonomers of the propylene copolymer fraction (B) areselected from the group consisting of C₅ α-olefin, C₆ α-olefin, C₇α-olefin, C₈ α-olefin, C₉ α-olefin, C₁₀ α-olefin, C₁₁ α-olefin, an C₁₂α-olefin, preferably the comonomers of the propylene copolymer fraction(B) are 1-hexene and/or 1-octene, more preferably the comonomer of thepropylene copolymer fraction (B) is 1-hexene only.

As mentioned above the polypropylene fraction (A) is the high molecularfraction whereas the propylene copolymer fraction (B) is the lowmolecular weight fraction. Therefore the polypropylene fraction (A) haspreferably a xylene cold soluble (XCS) content of below 2.0 wt.-%, morepreferably of below 1.5 wt.-%, still more preferably in the range of 0.3to 2.0 wt.-%, yet more preferably in the range of 0.5 to 1.5 wt.-%. Itis in particular preferred that the polypropylene fraction (A) has alower xylene cold soluble (XCS) content compared to the propylenecopolymer (C-PP).

Typically the polypropylene fraction (A), i.e. the propylene homopolymerfraction (H-A), has <2,1> regiodefects determined by ¹³C-spectroscopy ofequal or more than 0.4 mol.-%, more preferably of equal or more than 0.6mol.-%, like in the range of 0.7 to 0.9 mol.-%.

Further the invention is directed to the use of the instantpolypropylene composition as a film, like a cast film, an extrusionblown film or a biaxially oriented polypropylene (BOPP) film. Thepolypropylene composition of the present invention can be also used as acoating of an extrusion coated substrate.

Accordingly the invention is also directed to a film layer, preferablyto a sealing layer of a cast film, to an extrusion blown film or to abiaxially oriented polypropylene (BOPP) film, said film, i.e. film layer(sealing layer), the extrusion blown film or the biaxially orientedpolypropylene (BOPP) film, comprises at least 70 wt.-%, more preferablyat least 80 wt.-%, like at least 90 wt.-%, of the polypropylenecomposition according to the instant invention. In an especiallypreferred embodiment the film, i.e. the film layer (sealing layer) ofeither the extrusion blown film or the biaxially oriented polypropylene(BOPP) film, consists of the polypropylene composition as definedherein.

Further the present invention is directed to an extrusion coatedsubstrate comprising a coating, said coating comprises at least 70wt.-%, more preferably at least 90 wt.-%, like at least 95 wt.-%, of thepolypropylene composition according to the instant invention. In anespecially preferred embodiment the coating of the extrusion coatedsubstrate consists of the polypropylene composition as defined herein.The substrate can be for instance paper, paperboard, fabrics and metalfoils.

Additionally the present invention is directed to the preparation of thepropylene copolymer composition (P) of the instant invention.Accordingly, the polypropylene composition of the instant invention isin particular obtainable, preferably obtained, by a process as definedin detail below. In a first step the propylene homopolymer (H-PP) andthe propylene copolymer (C-PP) are produced separately and aresubsequently mixed, i.e. melt extruded.

The propylene homopolymer (H-PP) is produced in a known manner either inthe presence of a single-site catalyst or a Ziegler-Natta catalyst, thelatter is preferred. Concerning the polymerization in the presence of aZiegler-Natta catalyst it is referred to the patent applications EP 591224 A1 and EP 1 801 157 A1. With regard to a preferred process using asingle-site catalyst reference is made to the patent applications EP 1847 551 A1 and EP 1 847 552 A1.

The propylene copolymer (C-PP) is in particular obtainable, preferablyobtained, by a sequential polymerization process comprising at least tworeactors connected in series, wherein said process comprises the stepsof

-   (A) polymerizing in a first reactor (R-1) being a slurry reactor    (SR), preferably a loop reactor (LR), propylene and optionally at    least one C₅ to C₁₂ α-olefin, preferably 1-hexene, obtaining a    polypropylene fraction (A) as defined in the instant invention,    preferably as defined in claim 1 or 12,-   (B) transferring said polypropylene fraction (A) and unreacted    comonomers of the first reactor in a second reactor (R-2) being a    gas phase reactor (GPR-1),-   (C) feeding to said second reactor (R-2) propylene and at least one    C₅ to C₁₂ α-olefin,-   (D) polymerizing in said second reactor (R-2) and in the presence of    said polypropylene fraction (A) propylene and at least one C₅ to C₁₂    α-olefin obtaining a propylene copolymer fraction (B) as defined in    the instant invention, preferably as defined in claim 1 or 13, said    polypropylene fraction (A) and said propylene copolymer fraction (B)    form the propylene copolymer (C-PP) as defined in the instant    invention, preferably as defined in any one of the claims 1, 3, 10    and 11,    wherein further    in the first reactor (R-1) and second reactor (R-2) the    polymerization takes place in the presence of a solid catalyst    system (SCS), said solid catalyst system (SCS) comprises-   (i) a transition metal compound of formula (I)

R _(n)(Cp′)₂ MX ₂  (I)

-   -   wherein    -   “M” is zirconium (Zr) or hafnium (Hf),    -   each “X” is independently a monovalent anionic σ-ligand,    -   each “Cp′” is a cyclopentadienyl-type organic ligand        independently selected from the group consisting of substituted        cyclopentadienyl, substituted indenyl, substituted        tetrahydroindenyl, and substituted or unsubstituted fluorenyl,        said organic ligands coordinate to the transition metal (M),    -   “R” is a bivalent bridging group linking said organic ligands        (Cp′),    -   “n” is 1 or 2, preferably 1, and

-   (ii) optionally a cocatalyst (Co) comprising an element (E) of group    13 of the periodic table (IUPAC), preferably a cocatalyst (Co)    comprising a compound of Al.

Concerning the definition of the propylene copolymer (C-PP), thepolypropylene fraction (A) and the propylene copolymer fraction (B) itis referred to the definitions given above.

The term “sequential polymerization process” indicates that thepropylene copolymer (C-PP) is produced in at least two reactorsconnected in series. More precisely the “term sequential polymerizationprocess” indicates in the present application that the polymer of thefirst reactor (R-1) is directly conveyed with unreacted comonomers tothe second reactor (R-2). Accordingly decisive aspect of the presentprocess is the preparation of the propylene copolymer (C-PP) in twodifferent reactors, wherein the reaction material of the first reactor(R-1) is directly conveyed to the second reactor (R-2). Thus the presentprocess comprises at least a first reactor (R-1) and a second reactor(R-2). In one specific embodiment the instant process consists of twothe polymerization reactors (R-1) and (R-2). The term “polymerizationreactor” shall indicate that the main polymerization takes place. Thusin case the process consists of two polymerization reactors, thisdefinition does not exclude the option that the overall processcomprises for instance a pre-polymerization step in a pre-polymerizationreactor. The term “consists of” is only a closing formulation in view ofthe main polymerization reactors.

The first reactor (R-1) is preferably a slurry reactor (SR) and can becan be any continuous or simple stirred batch tank reactor or loopreactor operating in bulk or slurry. Bulk means a polymerization in areaction medium that comprises of at least 60% (wt/wt), preferably 100%monomer. According to the present invention the slurry reactor (SR) ispreferably a (bulk) loop reactor (LR).

The second reactor (R-2) and any subsequent reactor are preferably gasphase reactors (GPR). Such gas phase reactors (GPR) can be anymechanically mixed or fluid bed reactors. Preferably the gas phasereactor s (GPR) comprise a mechanically agitated fluid bed reactor withgas velocities of at least 0.2 m/sec. Thus it is appreciated that thegas phase reactor is a fluidized bed type reactor preferably with amechanical stirrer.

The condition (temperature, pressure, reaction time, monomer feed) ineach reactor is dependent on the desired product which is in theknowledge of a person skilled in the art. As already indicated above,the first reactor (R-1) is preferably a slurry reactor (SR), like a loopreactor (LR), whereas the second reactor (R-2) is preferably a gas phasereactor (GPR-1). The subsequent reactors—if present—are also preferablygas phase reactors (GPR).

A preferred multistage process is a “loop-gas phase”-process, such asdeveloped by Borealis A/S, Denmark (known as BORSTAR® technology)described e.g. in patent literature, such as in EP 0 887 379 or in WO92/12182.

Multimodal polymers can be produced according to several processes whichare described, e.g. in WO 92/12182, EP 0 887 379, and WO 98/58976. Thecontents of these documents are included herein by reference.

Preferably, in the instant process for producing propylene copolymer(C-PP) as defined above the conditions for the first reactor (R-1), i.e.the slurry reactor (SR), like a loop reactor (LR), of step (A) may be asfollows:

-   -   the temperature is within the range of 40° C. to 110° C.,        preferably between 60° C. and 100° C., 70 to 90° C.,    -   the pressure is within the range of 20 bar to 80 bar, preferably        between 40 bar to 70 bar,    -   hydrogen can be added for controlling the molar mass in a manner        known per se.

Subsequently, the reaction mixture from step (A) is transferred to thesecond reactor (R-2), i.e. gas phase reactor (GPR-1), i.e. to step (D),whereby the conditions in step (D) are preferably as follows:

-   -   the temperature is within the range of 50° C. to 130° C.,        preferably between 60° C. and 100° C.,    -   the pressure is within the range of 5 bar to 50 bar, preferably        between 15 bar to 40 bar,    -   hydrogen can be added for controlling the molar mass in a manner        known per se.

The residence time can vary in both reactor zones.

In one embodiment of the process for producing the propylene copolymer(C-PP) the residence time in bulk reactor, e.g. loop is in the range 0.2to 4 hours, e.g. 0.3 to 1.5 hours and the residence time in gas phasereactor will generally be 0.2 to 6.0 hours, like 0.5 to 4.0 hours.

If desired, the polymerization may be effected in a known manner undersupercritical conditions in the first reactor (R-1), i.e. in the slurryreactor (SR), like in the loop reactor (LR), and/or as a condensed modein the gas phase reactor (GPR-1).

The conditions in the other gas phase reactors (GPR), if present, aresimilar to the second reactor (R-2).

The present process may also encompass a pre-polymerization prior to thepolymerization in the first reactor (R-1). The pre-polymerization can beconducted in the first reactor (R-1), however it is preferred that thepre-polymerization takes place in a separate reactor, so calledpre-polymerization reactor.

In one specific embodiment the solid catalyst system (SCS) has aporosity measured according ASTM 4641 of less than 1.40 ml/g and/or asurface area measured according to ASTM D 3663 of lower than 25 m²/g.

Preferably the solid catalyst system (SCS) has a surface area of lowerthan 15 m²/g, yet still lower than 10 m²/g and most preferred lower than5 m²/g, which is the lowest measurement limit. The surface areaaccording to this invention is measured according to ASTM D 3663 (N₂)

Alternatively or additionally it is appreciated that the solid catalystsystem (SCS) has a porosity of less than 1.30 ml/g and more preferablyless than 1.00 ml/g. The porosity has been measured according to ASTM4641 (N₂). In another preferred embodiment the porosity is notdetectable when determined with the method applied according to ASTM4641 (N₂).

Furthermore the solid catalyst system (SCS) typically has a meanparticle size of not more than 500 μm, i.e. preferably in the range of 2to 500 μm, more preferably 5 to 200 μm. It is in particular preferredthat the mean particle size is below 80 μm, still more preferably below70 μm. A preferred range for the mean particle size is 5 to 70 μm, oreven 10 to 60 μm.

As stated above the transition metal (M) is zirconium (Zr) or hafnium(Hf), preferably zirconium (Zr).

The term “σ-ligand” is understood in the whole description in a knownmanner, i.e. a group bound to the metal via a sigma bond. Thus theanionic ligands “X” can independently be halogen or be selected from thegroup consisting of R′, OR′, SiR′₃, OSiR′₃, OSO₂CF₃, OCOR′, SR′, NR′₂ orPR′₂ group wherein R′ is independently hydrogen, a linear or branched,cyclic or acyclic, C₁ to C₂₀ alkyl, C₂ to C₂₀ alkenyl, C₂ to C₂₀alkynyl, C₃ to C₁₂ cycloalkyl, C₆ to C₂₀ aryl, C₇ to C₂₀ arylalkyl, C₇to C₂₀ alkylaryl, C₈ to C₂₀ arylalkenyl, in which the R′ group canoptionally contain one or more heteroatoms belonging to groups 14 to 16.In a preferred embodiments the anionic ligands “X” are identical andeither halogen, like Cl, or methyl or benzyl.

A preferred monovalent anionic ligand is halogen, in particular chlorine(Cl).

The substituted cyclopentadienyl-type ligand(s) may have one or moresubstituent(s) being selected from the group consisting of halogen,hydrocarbyl (e.g. C₁ to C₂₀ alkyl, C₂ to C₂₀ alkenyl, C₂ to C₂₀ alkynyl,C₃ to C₂₀ cycloalkyl, like C₁ to C₂₀ alkyl substituted C₅ to C₂₀cycloalkyl, C₆ to C₂₀ aryl, C₅ to C₂₀ cycloalkyl substituted C₁ to C₂₀alkyl wherein the cycloalkyl residue is substituted by C₁ to C₂₀ alkyl,C₇ to C₂₀ arylalkyl, C₃ to C₁₂ cycloalkyl which contains 1, 2, 3 or 4heteroatom(s) in the ring moiety, C₆ to C₂₀-heteroaryl, C₁ toC₂₀-haloalkyl, —SiR″₃, —SR″, —PR″₂ or —NR″₂, each R″ is independently ahydrogen or hydrocarbyl (e.g. C₁ to C₂₀ alkyl, C₁ to C₂₀ alkenyl, C₂ toC₂₀ alkynyl, C₃ to C₁₂ cycloalkyl, or C₆ to C₂₀ aryl) or e.g. in case of—NR″₂, the two substituents R″ can form a ring, e.g. five- orsix-membered ring, together with the nitrogen atom wherein they areattached to.

Further “R” of formula (I) is preferably a bridge of 1 to 4 atoms, suchatoms being independently carbon (C), silicon (Si), germanium (Ge) oroxygen (O) atom(s), whereby each of the bridge atoms may bearindependently substituents, such as C₁ to C₂₀-hydrocarbyl, tri(C₁ toC₂₀-alkyl)silyl, tri(C₁ to C₂₀-alkyl)siloxy and more preferably “R” is aone atom bridge like e.g. —SiR′″₂—, wherein each R′″ is independently C₁to C₂₀-alkyl, C₂ to C₂₀-alkenyl, C₂ to C₂₀-alkynyl, C₃ to C₁₂cycloalkyl, C₆ to C₂₀-aryl, alkylaryl or arylalkyl, or tri(C₁ to C₂₀alkyl)silyl-residue, such as trimethylsilyl-, or the two R′″ can be partof a ring system including the Si bridging atom.

In a preferred embodiment the transition metal compound has the formula(II)

wherein

-   M is zirconium (Zr) or hafnium (Hf), preferably zirconium (Zr),-   X are ligands with a σ-bond to the metal “M”, preferably those as    defined above for formula (I),    -   preferably chlorine (Cl) or methyl (CH₃), the former especially        preferred,-   R¹ are equal to or different from each other, preferably equal to,    and are selected from the group consisting of linear saturated C₁ to    C₂₀ alkyl, linear unsaturated C₁ to C₂₀ alkyl, branched saturated    C₁-C₂₀ alkyl, branched unsaturated C₁ to C₂₀ alkyl, C₃ to C₂₀    cycloalkyl, C₆ to C₂₀ aryl, C₇ to C₂₀ alkylaryl, and C₇ to C₂₀    arylalkyl, optionally containing one or more heteroatoms of groups    14 to 16 of the Periodic Table (IUPAC),    -   preferably are equal to or different from each other, preferably        equal to, and are C₁ to C₁₀ linear or branched hydrocarbyl, more        preferably are equal to or different from each other, preferably        equal to, and are C₁ to C₆ linear or branched alkyl,-   R² to R⁶ are equal to or different from each other and are selected    from the group consisting of hydrogen, linear saturated C₁-C₂₀    alkyl, linear unsaturated C₁-C₂₀ alkyl, branched saturated C₁-C₂₀    alkyl, branched unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀    aryl, C₇-C₂₀ alkylaryl, and C₇-C₂₀ arylalkyl, optionally containing    one or more heteroatoms of groups 14 to 16 of the Periodic Table    (IUPAC),    -   preferably are equal to or different from each other and are C₁        to C₁₀ linear or branched hydrocarbyl, more preferably are equal        to or different from each other and are C₁ to C₆ linear or        branched alkyl,-   R⁷ and R⁸ are equal to or different from each other and selected    from the group consisting of hydrogen, linear saturated C₁ to C₂₀    alkyl, linear unsaturated C₁ to C₂₀ alkyl, branched saturated C₁ to    C₂₀ alkyl, branched unsaturated C₁ to C₂₀ alkyl, C₃ to C₂₀    cycloalkyl, C₆ to C₂₀ aryl, C₇ to C₂₀ alkylaryl, C₇ to C₂₀    arylalkyl, optionally containing one or more heteroatoms of groups    14 to 16 of the Periodic Table (IUPAC), SiR¹⁰ ₃, GeR¹⁰ ₃, OR¹⁰, SR¹⁰    and NR¹⁰ ₂,    -   wherein    -   R¹⁰ is selected from the group consisting of linear saturated        C₁-C₂₀ alkyl, linear unsaturated C₁ to C₂₀ alkyl, branched        saturated C₁ to C₂₀ alkyl, branched unsaturated C₁ to C₂₀ alkyl,        C₃ to C₂₀ cycloalkyl, C₆ to C₂₀ aryl, C₇ to C₂₀ alkylaryl, and        C₇ to C₂₀ arylalkyl, optionally containing one or more        heteroatoms of groups 14 to 16 of the Periodic Table (IUPAC),    -   and/or    -   R⁷ and R⁸ being optionally part of a C₄ to C₂₀ carbon ring        system together with the indenyl carbons to which they are        attached, preferably a C₅ ring, optionally one carbon atom can        be substituted by a nitrogen, sulfur or oxygen atom,-   R⁹ are equal to or different from each other and are selected from    the group consisting of hydrogen, linear saturated C₁ to C₂₀ alkyl,    linear unsaturated C₁ to C₂₀ alkyl, branched saturated C₁ to C₂₀    alkyl, branched unsaturated C₁ to C₂₀ alkyl, C₃ to C₂₀ cycloalkyl,    C₆ to C₂₀ aryl, C₇ to C₂₀ alkylaryl, C₇ to C₂₀ arylalkyl, OR¹⁰, and    SR¹⁰,    -   preferably R⁹ are equal to or different from each other and are        H or CH₃,    -   wherein    -   R¹⁰ is defined as before,-   L is a bivalent group bridging the two indenyl ligands, preferably    being a C₂R¹¹ ₄ unit or a SiR¹¹ ₂ or GeR¹¹ ₂, wherein,    -   R¹¹ is selected from the group consisting of H, linear saturated        C₁ to C₂₀ alkyl, linear unsaturated C₁ to C₂₀ alkyl, branched        saturated C₁ to C₂₀ alkyl, branched unsaturated C₁ to C₂₀ alkyl,        C₃ to C₂₀ cycloalkyl, C₆ to C₂₀ aryl, C₇ to C₂₀ alkylaryl or C₇        to C₂₀ arylalkyl, optionally containing one or more heteroatoms        of groups 14 to 16 of the Periodic Table (IUPAC),    -   preferably Si(CH₃)₂, SiCH₃C₆H₁₁, or SiPh₂,    -   wherein C₆H₁₁ is cyclohexyl.

Preferably the transition metal compound of formula (II) is C₂-symmetricor pseudo-C₂-symmetric. Concerning the definition of symmetry it isreferred to Resconi et al. Chemical Reviews, 2000, Vol. 100, No. 4 1263and references herein cited.

Preferably the residues R¹ are equal to or different from each other,more preferably equal, and are selected from the group consisting oflinear saturated C₁ to C₁₀ alkyl, linear unsaturated C₁ to C₁₀ alkyl,branched saturated C₁ to C₁₀ alkyl, branched unsaturated C₁ to C₁₀ alkyland C₇ to C₁₂ arylalkyl. Even more preferably the residues R¹ are equalto or different from each other, more preferably equal, and are selectedfrom the group consisting of linear saturated C₁ to C₆ alkyl, linearunsaturated C₁ to C₆ alkyl, branched saturated C₁ to C₆ alkyl, branchedunsaturated C₁ to C₆ alkyl and C₇ to C₁₀ arylalkyl. Yet more preferablythe residues R¹ are equal to or different from each other, morepreferably equal, and are selected from the group consisting of linearor branched C₁ to C₄ hydrocarbyl, such as for example methyl or ethyl.

Preferably the residues R² to R⁶ are equal to or different from eachother and linear saturated C₁ to C₄ alkyl or branched saturated C₁ to C₄alkyl. Even more preferably the residues R² to R⁶ are equal to ordifferent from each other, more preferably equal, and are selected fromthe group consisting of methyl, ethyl, iso-propyl and tert-butyl.

Preferably R⁷ and R⁸ are equal to or different from each other and areselected from hydrogen and methyl, or they are part of a 5-methylenering including the two indenyl ring carbons to which they are attached.In another preferred embodiment, R⁷ is selected from OCH₃ and OC₂H₅, andR⁸ is tert-butyl.

In a preferred embodiment the transition metal compound israc-methyl(cyclohexyl)silanediylbis(2-methyl-4-(4-tert-butylphenyl)indenyl)zirconium dichloride.

In a second preferred embodiment, the transition metal compound israc-dimethylsilanediylbis(2-methyl-4-phenyl-1,5,6,7-tetrahydro-s-indacen-1-yl)zirconiumdichloride.

In a third preferred embodiment, the transition metal compound israc-dimethylsilanediylbis(2-methyl-4-phenyl-5-methoxy-6-tert-butylindenyl)zirconiumdichloride.

As a further requirement the solid catalyst system (SCS) according tothis invention must comprise a cocatalyst (Co) comprising an element (E)of group 13 of the periodic table (IUPAC), for instance the cocatalyst(Co) comprises a compound of Al.

Examples of such cocatalyst (Co) are organo aluminium compounds, such asaluminoxane compounds.

Such compounds of Al, preferably aluminoxanes, can be used as the onlycompound in the cocatalyst (Co) or together with other cocatalystcompound(s). Thus besides or in addition to the compounds of Al, i.e.the aluminoxanes, other cation complex forming cocatalyst compounds,like boron compounds can be used. Said cocatalysts are commerciallyavailable or can be prepared according to the prior art literature.Preferably however in the manufacture of the solid catalyst system onlycompounds of Al as cocatalyst (Co) are employed.

In particular preferred cocatalysts (Co) are the aluminoxanes, inparticular the C1 to C10-alkylaluminoxanes, most particularlymethylaluminoxane (MAO).

Preferably, the organo-zirconium compound of formula (I) and thecocatalyst (Co) of the solid catalyst system (SCS) represent at least 70wt %, more preferably at least 80 wt %, even more preferably at least 90wt %, even further preferably at least 95 wt % of the solid catalystsystem. Thus it is appreciated that the solid catalyst system isfeatured by the fact that it is self-supported, i.e. it does notcomprise any catalytically inert support material, like for instancesilica, alumina or MgCl₂ or porous polymeric material, which isotherwise commonly used in heterogeneous catalyst systems, i.e. thecatalyst is not supported on external support or carrier material. As aconsequence of that the solid catalyst system (SCS) is self-supportedand it has a rather low surface area.

In one embodiment the solid metallocene catalyst system (SCS) isobtained by the emulsion solidification technology, the basic principlesof which are described in WO 03/051934. This document is herewithincluded in its entirety by reference.

Hence the solid catalyst system (SCS) is preferably in the form of solidcatalyst particles, obtainable by a process comprising the steps of

-   a) preparing a solution of one or more catalyst components;-   b) dispersing said solution in a second solvent to form an emulsion    in which said one or more catalyst components are present in the    droplets of the dispersed phase,-   c) solidifying said dispersed phase to convert said droplets to    solid particles and optionally recovering said particles to obtain    said catalyst.

Preferably a first solvent, more preferably a first organic solvent, isused to form said solution. Still more preferably the organic solvent isselected from the group consisting of a linear alkane, cyclic alkane,aromatic hydrocarbon and halogen-containing hydrocarbon.

Moreover the second solvent forming the continuous phase is an inertsolvent towards to catalyst components, The second solvent might beimmiscible towards the solution of the catalyst components at leastunder the conditions (like temperature) during the dirpersing step. Theterm “immiscible with the catalyst solution” means that the secondsolvent (continuous phase) is fully immiscible or partly immiscible i.e.not fully miscible with the dispersed phase solution.

Preferably the immiscible solvent comprises a fluorinated organicsolvent and/or a functionalized derivative thereof, still morepreferably the immiscible solvent comprises a semi-, highly- orperfluorinated hydrocarbon and/or a functionalized derivative thereof.It is in particular preferred, that said immiscible solvent comprises aperfluorohydrocarbon or a functionalized derivative thereof, preferablyC₃-C₃₀ perfluoroalkanes, -alkenes or -cycloalkanes, more preferredC₄-C₁₀ perfluoro-alkanes, -alkenes or -cycloalkanes, particularlypreferred perfluorohexane, perfluoroheptane, perfluorooctane orperfluoro (methylcyclohexane) or perfluoro (1,3-dimethylcyclohexane or amixture thereof.

Furthermore it is preferred that the emulsion comprising said continuousphase and said dispersed phase is a bi- or multiphasic system as knownin the art. An emulsifier may be used for forming and stabilising theemulsion. After the formation of the emulsion system, said catalyst isformed in situ from catalyst components in said solution.

In principle, the emulsifying agent may be any suitable agent whichcontributes to the formation and/or stabilization of the emulsion andwhich does not have any adverse effect on the catalytic activity of thecatalyst. The emulsifying agent may e.g. be a surfactant based onhydrocarbons optionally interrupted with (a) heteroatom(s), preferablyhalogenated hydrocarbons optionally having a functional group,preferably semi-, highly- or perfluorinated hydrocarbons as known in theart. Alternatively, the emulsifying agent may be prepared during theemulsion preparation, e.g. by reacting a surfactant precursor with acompound of the catalyst solution. Said surfactant precursor may be ahalogenated hydrocarbon with at least one functional group, e.g. ahighly fluorinated C1-n (suitably C4-30- or C5-15) alcohol (e.g. highlyfluorinated heptanol, octanol or nonanol), oxide (e.g. propenoxide) oracrylate ester which reacts e.g. with a cocatalyst component, such asaluminoxane to form the “actual” surfactant.

In principle any solidification method can be used for forming the solidparticles from the dispersed droplets. According to one preferableembodiment the solidification is effected by a temperature changetreatment. Hence the emulsion subjected to gradual temperature change ofup to 10° C./min, preferably 0.5 to 6° C./min and more preferably 1 to5° C./min. Even more preferred the emulsion is subjected to atemperature change of more than 40° C., preferably more than 50° C.within less than 10 seconds, preferably less than 6 seconds.

For further details, embodiments and examples of the continuous anddispersed phase system, emulsion formation method, emulsifying agent andsolidification methods reference is made e.g. to the above citedinternational patent application WO 03/051934.

All or part of the preparation steps can be done in a continuous manner.Reference is made to WO 2006/069733 describing principles of such acontinuous or semicontinuous preparation methods of the solid catalysttypes, prepared via emulsion/solidification method.

The above described catalyst components are prepared according to themethods described in WO 01/48034.

More over the present invention is related to the manufacture of theextrusion coated substrates by conventional extrusion coating of thepolypropylene composition as defined herein.

The film according to this invention can be obtained in a conventionalmanner for instance by cast film technology or extrusion blown filmtechnology. In case the film shall be stretched, i.e. a biaxiallyoriented polypropylene film, it is produced preferably as follows:first, a cast film is prepared by extrusion of polypropylene compositionin the form of pellets. The prepared cast films may typically have athickness of 50 to 100 μm as used for further film stretching.Subsequently, a stack of cast films can be prepared from a number ofcast film sheets to achieve a specific stack thickness, e.g. 700 to 1000μm. The stretching temperature is typically set to a temperatureslightly below the melting point, e.g. 2 to 4° C. below the meltingpoint, and the film is stretched at a specific draw ratio in machinedirection and transverse direction.

The extrusion coating process may be carried out using conventionalextrusion coating techniques. Hence, the polypropylene compositionobtained from the above defined process is fed, typically in the form ofpellets, optionally containing additives, to an extruding device. Fromthe extruder the polymer melt is passed preferably through a flat die tothe substrate to be coated. Due to the distance between the die lip andthe nip, the molten plastic is oxidized in the air for a short period,usually leading to an improved adhesion between the coating and thesubstrate. The coated substrate is cooled on a chill roll, after whichit is passed to edge trimmers and wound up. The width of the line mayvary between, for example, 500 to 1500 mm, e.g. 800 to 1100 mm, with aline speed of up to 1000 m/min, for instance 300 to 800 m/min. Thetemperature of the polymer melt is typically between 275 and 330° C. Thepolypropylene composition of the invention can be extruded onto thesubstrate as a monolayer coating or as one layer in coextrusion. Ineither of these cases it is possible to use the polypropylenecomposition as such or to blend the polypropylene composition with otherpolymers. Blending can occur in a post reactor treatment or just priorto the extrusion in the coating process. However it is preferred thatonly the polypropylene composition as defined in the present inventionis extrusion coated. In a multilayer extrusion coating, the other layersmay comprise any polymer resin having the desired properties andprocessability. Examples of such polymers include: barrier layer PA(polyamide) and EVA; polar copolymers of ethylene, such as copolymers ofethylene and vinyl alcohol or copolymers of ethylene and an acrylatemonomer; adhesive layers, e.g. ionomers, copolymers of ethylene andethyl acrylate, etc; HDPE for stiffness; LDPE resins produced in ahigh-pressure process; LLDPE resins produced by polymerising ethyleneand alpha-olefin comonomers in the presence of a Ziegler, chromium ormetallocene catalyst; and MDPE resins.

Thus the present invention is preferably related to extrusion coatedsubstrates comprising a substrate and at least one layer of thepolypropylene composition extrusion coated on said substrate as definedin this invention.

Furthermore the present invention is also directed to the use of theinventive article as packing material, in particular as a packingmaterial for food and/or medical products.

In the following, the present invention is described by way of examples.

EXAMPLES A. Measuring Methods

The following definitions of terms and determination methods apply forthe above general description of the invention as well as to the belowexamples unless otherwise defined.

Quantification of Microstructure by NMR Spectroscopy

Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used toquantify the isotacticity, regio-regularity and comonomer content of thepolymers.

Quantitative ¹³C{¹H} NMR spectra were recorded in the solution-stateusing a Bruker Advance III 400 NMR spectrometer operating at 400.15 and100.62 MHz for ¹H and ¹³C respectively. All spectra were recorded usinga ¹³C optimised 10 mm extended temperature probehead at 125° C. usingnitrogen gas for all pneumatics.

For polypropylene homopolymers approximately 200 mg of material wasdissolved in 1,2-tetrachloroethane-d₂ (TCE-d₂). To ensure a homogenoussolution, after initial sample preparation in a heat block, the NMR tubewas further heated in a rotatary oven for at least 1 hour. Uponinsertion into the magnet the tube was spun at 10 Hz. This setup waschosen primarily for the high resolution needed for tacticitydistribution quantification (Busico, V., Cipullo, R., Prog. Polym. Sci.26 (2001) 443; Busico, V.; Cipullo, R., Monaco, G., Vacatello, M.,Segre, A. L., Macromoleucles 30 (1997) 6251). Standard single-pulseexcitation was employed utilising the NOE and bi-level WALTZ 16decoupling scheme (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong,R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225;Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J.,Talarico, G., Macromol. Rapid Commun. 2007, 28, 11289). A total of 8192(8 k) transients were acquired per spectra

For ethylene-propylene copolymers approximately 200 mg of material wasdissolved in 3 ml of 1,2-tetrachloroethane-d₂ (TCE-d₂) along withchromium-(III)-acetylacetonate (Cr(acac)₃) resulting in a 65 mM solutionof relaxation agent in solvent (Singh, G., Kothari, A., Gupta, V.,Polymer Testing 28 5 (2009), 475). To ensure a homogenous solution,after initial sample preparation in a heat block, the NMR tube wasfurther heated in a rotatary oven for at least 1 hour. Upon insertioninto the magnet the tube was spun at 10 Hz. This setup was chosenprimarily for the high resolution and quantitatively needed for accurateethylene content quantification. Standard single-pulse excitation wasemployed without NOE, using an optimised tip angle, 1 s recycle delayand a bi-level WALTZ 16 decoupling scheme(Zhou, Z., Kuemmerle, R., Qiu,X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag.Reson. 187 (2007) 225; Busico, V., Carbonniere, P., Cipullo, R.,Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007,28, 11289). A total of 6144 (6 k) transients were acquired per spectra.

Quantitative ¹³C{¹H} NMR spectra were processed, integrated and relevantquantitative properties determined from the integrals using proprietarycomputer programs.

For ethylene-propylene copolymers all chemical shifts were indirectlyreferenced to the central methylene group of the ethylene block (EEE) at30.00 ppm using the chemical shift of the solvent. This approach allowedcomparable referencing even when this structural unit was not present.

For polypropylene homopolymers all chemical shifts are internallyreferenced to the methyl isotactic pentad (mmmm) at 21.85 ppm.

Characteristic signals corresponding to regio defects (Resconi, L.,Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253; Wang,W-J., Zhu, S., Macromolecules 33 (2000), 1157; Cheng, H. N.,Macromolecules 17 (1984), 1950) or comonomer were observed.

The tacticity distribution was quantified through integration of themethyl region between 23.6-19.7 ppm correcting for any sites not relatedto the stereo sequences of interest (Busico, V., Cipullo, R., Prog.Polym. Sci. 26 (2001) 443; Busico, V., Cipullo, R., Monaco, G.,Vacatello, M., Segre, A. L., Macromoleucles 30 (1997) 6251).

Specifically the influence of regio defects and comonomer on thequantification of the tacticity distribution was corrected for bysubtraction of representative regio defect and comonomer integrals fromthe specific integral regions of the stereo sequences. The isotacticitywas determined at the pentad level and reported as the percentage ofisotactic pentad (mmmm) sequences with respect to all pentad sequences:

[mmmm]%=100*(mmmm/sum of all pentads)

The presence of 2,1 erythro regio defects was indicated by the presenceof the two methyl sites at 17.7 and 17.2 ppm and confirmed by othercharacteristic sites. Characteristic signals corresponding to othertypes of regio defects were not observed (Resconi, L., Cavallo, L.,Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253).

The amount of 2,1 erythro regio defects was quantified using the averageintegral of the two characteristic methyl sites at 17.7 and 17.2 ppm:

P _(21e)=(I _(e6) +I _(e8))/2

The amount of 1,2 primary inserted propene was quantified based on themethyl region with correction undertaken for sites included in thisregion not related to primary insertion and for primary insertion sitesexcluded from this region:

P ₁₂ I _(CH3) +P _(12e)

The total amount of propene was quantified as the sum of primaryinserted propene and all other present regio defects:

P _(total) =P ₁₂ +P _(21e)

The mole percent of 2,1 erythro regio defects was quantified withrespect to all propene:

[21e]mol %=100*(P _(21e) /P _(total))

For copolymers characteristic signals corresponding to the incorporationof ethylene were observed (Cheng, H. N., Macromolecules 17 (1984),1950).

With regio defects also observed (Resconi, L., Cavallo, L., Fait, A.,Piemontesi, F., Chem. Rev. 2000, 100, 1253; Wang, W-J., Zhu, S.,Macromolecules 33 (2000), 1157; Cheng, H. N., Macromolecules 17 (1984),1950) correction for the influence of such defects on the comonomercontent was required.

The mole fraction of ethylene in the polymer was quantified using themethod of Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000),1157) through integration of multiple signals across the whole spectralregion of a ¹³C{₁H} spectra acquired using defined conditions. Thismethod was chosen for its accuracy, robust nature and ability to accountfor the presence of regio-defects when needed. Integral regions wereslightly adjusted to increase applicability to a wider range ofcomonomer contents.

The mole percent comonomer incorporation in the polymer was calculatedfrom the mole fraction according to:

E[mol %]=100*fE

The weight percent comonomer incorporation in the polymer was calculatedfrom the mole fraction according to:

E[wt %]=100*(fE*28.05)/((fE*28.05)+((14E)*42.08))

The comonomer sequence distribution at the triad level was determinedusing the method of Kakugo et al. (Kakugo, M., Naito, Y., Mizunuma, K.,Miyatake, T. Macromolecules 15 (1982) 1150) through integration ofmultiple signals across the whole spectral region of a ¹³C{¹H} spectraacquired using defined conditions. This method was chosen for its robustnature. Integral regions were slightly adjusted to increaseapplicability to a wider range of comonomer contents.

The mole percent of a given comonomer triad sequence in the polymer wascalculated from the mole fraction determined by the method of Kakugo etat. (Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15(1982) 1150) according to:

XXX[mol %]=100*fXXX

The mole fraction comonomer incorporation in the polymer, as determinedfrom the comonomer sequence distribution at the triad level, werecalculated from the triad distribution using known necessaryrelationships (Randall, J. Macromol. Sci., Rev. Macromol. Chem. Phys.1989, C29, 201):

fXEX=fEEE+fPEE+fPEP

fXPX=fPPP+fEPP+fEPE

where PEE and EPP represents the sum of the reversible sequences PEE/EEPand EPP/PPE respectively.

The randomness of the comonomer distribution was quantified as therelative amount of isolated ethylene sequences as compared to allincorporated ethylene. The randomness was calculated from the triadsequence distribution using the relationship:

R(E)[%]=100*(fPEP/fXEX)

Characteristic signals corresponding to the incorporation of 1-hexenewere observed, and the 1-hexene content was calculated as the molepercent of 1-hexene in the polymer, H(mol %), according to:

[H]=H _(tot)/(P _(tot) +H _(tot))

where:

H _(tot) =I(αB ₄)/2+I(ααB ₄)×2

where I(αB₄) is the integral of the αB₄ sites at 44.1 ppm, whichidentifies the isolated 1-hexene incorporated in PPHPP sequences, andI(ααB₄) is the integral of the ααB₄ sites at 41.6 ppm, which identifiesthe consecutively incorporated 1-hexene in PPHHPP sequences.P_(tot)=Integral of all CH3 areas on the methyl region with correctionapplied for underestimation of other propene units not accounted for inthis region and overestimation due to other sites found in this region.

and H(mol %)=100×[H]

which is then converted into wt % using the correlation

H(wt %)=(100×H mol %×84.16)/(H mol %×84.16+(100−H mol %)×42.08)

A statistical distribution is suggested from the relationship betweenthe content of hexene present in isolated (PPHPP) and consecutive(PPHHPP) incorporated comonomer sequences:

[HH]<[H] ²

Calculation of comonomer content of the propylene copolymer fraction(B):

$\frac{{C({CPP})} - {{w(A)}{{xC}(A)}}}{w(B)} = {C(B)}$

wherein

-   w(A) is the weight fraction of the polypropylene fraction (A),-   w(B) is the weight fraction of the propylene copolymer fraction (B),-   C(A) is the comonomer content [in wt.-%] measured by Fourier    transform infrared spectroscopy (FTIR) of the polypropylene fraction    (A), i.e. of the product of the first reactor (R1),-   C(CPP) is the comonomer content [in wt.-%] measured by Fourier    transform infrared spectroscopy (FTIR) of the product obtained in    the second reactor (R2), i.e. the mixture of the polypropylene    fraction (A) and the propylene copolymer fraction (B) [of the    propylene copolymer (C-PP)],-   C(B) is the calculated comonomer content [in wt.-%] of the propylene    copolymer fraction (B)

Mw, Mn, MWD

Mw/Mn/MWD are measured by Gel Permeation Chromatography (GPC) accordingto the following method:

The weight average molecular weight (Mw), the number average molecularweight (Mn), and the molecular weight distribution (MWD=Mw/Mn) ismeasured by a method based on ISO 16014-1:2003 and ISO 16014-4:2003. AWaters Alliance GPCV 2000 instrument, equipped with refractive indexdetector and online viscosimeter is used with 3×TSK-gel columns(GMHXL-HT) from TosoHaas and 1,2,4-trichlorobenzene (TCB, stabilizedwith 200 mg/L 2,6-Di tert butyl-4-methyl-phenol) as solvent at 145° C.and at a constant flow rate of 1 mL/min. 216.5 μL of sample solution areinjected per analysis. The column set is calibrated using relativecalibration with 19 narrow MWD polystyrene (PS) standards in the rangeof 0.5 kg/mol to 11 500 kg/mol and a set of well characterized broadpolypropylene standards. All samples are prepared by dissolving 5 to 10mg of polymer in 10 mL (at 160° C.) of stabilized TCB (same as mobilephase) and keeping for 3 hours with continuous shaking prior sampling ininto the GPC instrument.

Melt Flow Rate (MFR)

The melt flow rates are measured with a load of 2.16 kg (MFR₂) at 230°C. The melt flow rate is that quantity of polymer in grams which thetest apparatus standardised to ISO 1133 extrudes within 10 minutes at atemperature of 230° C. under a load of 2.16 kg.

Calculation of melt flow rate MFR₂ (230° C.) of the propylene copolymerfraction (B):

${{MFR}(B)} = 10^{\lbrack\frac{{\log {({{MFR}{(P)}})}} - {{w{(A)}}x\mspace{14mu} {\log {({{MFR}{(A)}})}}}}{w{(B)}}\rbrack}$

wherein

-   w(A) is the weight fraction of the propylene copolymer fraction (A),-   w(B) is the weight fraction of the propylene copolymer fraction (B),-   MFR(A) is the melt flow rate MFR₂ (230° C.) [in g/10 min] measured    according ISO 1133 of the propylene copolymer fraction (A),-   MFR(P) is the melt flow rate MFR₂ (230° C.) [in g/10 min] measured    according ISO 1133 of the propylene copolymer (C-PP),-   MFR(B) is the calculated melt flow rate MFR₂ (230° C.) [in g/10 min]    of the propylene copolymer fraction (B).

Xylene Cold Soluble Fraction (XCS Wt %)

The xylene cold soluble fraction (XCS) is determined at 23° C. accordingto ISO 6427. Calculation of the xylene cold soluble (XCS) content of thepropylene copolymer fraction (B):

$\frac{{{XS}({CPP})} - {{w(A)}{{xXS}(A)}}}{w(B)} = {{XS}(B)}$

wherein

-   w(A) is the weight fraction of the polypropylene fraction (A), i.e.    the product of the first reactor (R1),-   w(B) is the weight fraction of the propylene copolymer fraction (B),    i.e. of the polymer produced in the second reactor (R2),-   XS(A) is the xylene cold soluble (XCS) content [in wt.-%] as    determined at 23° C. according to ISO 6427 of the polypropylene    fraction (A), i.e. of the product of the first reactor (R1),-   XS(CPP) is the xylene cold soluble (XCS) content [in wt.-%] as    determined at 23° C. according to ISO 6427 of the product obtained    in the second reactor (R2), i.e. the mixture of the polypropylene    fraction (A) and the propylene copolymer fraction (B) [of the    propylene copolymer (C-PP)],-   XS(B) is the calculated xylene cold soluble (XCS) content [in wt.-%]    of the propylene copolymer fraction (B)

Melting temperature T_(m), crystallization temperature T_(c), ismeasured with Mettler TA820 differential scanning calorimetry (DSC) on5-10 mg samples. Both crystallization and melting curves were obtainedduring 10° C./min cooling and heating scans between 30° C. and 225° C.Melting and crystallization temperatures were taken as the peaks ofendotherms and exotherms.

Also the melt- and crystallization enthalpy (Hm and Hc) were measured bythe DSC method according to ISO 11357-3.

Porosity: BET with N₂ gas, ASTM 4641, apparatus Micromeritics Tristar3000; sample preparation: at a temperature of 50° C., 6 hours in vacuum.Surface area: BET with N₂ gas ASTM D 3663, apparatus MicromeriticsTristar 3000: sample preparation at a temperature of 50° C., 6 hours invacuum.Sealing initiation temperature (SIT); sealing end temperature (SET),sealing range: The method determines the sealing temperature range(sealing range) of polypropylene films, in particular blown films orcast films. The sealing temperature range is the temperature range, inwhich the films can be sealed according to conditions given below. Thelower limit (heat sealing initiation temperature (SIT)) is the sealingtemperature at which a sealing strength of >3 N is achieved. The upperlimit (sealing end temperature (SET)) is reached, when the films stickto the sealing device.

The sealing range is determined on a J&B Universal Sealing Machine Type3000 with an extrusion cast film of 100 μm thickness with the followingfurther parameters:

Specimen width: 25.4 mm

Seal Pressure: 0.1 N/mm² Seal Time: 0.1 sec

Cool time: 99 secPeel Speed: 10 mm/secStart temperature: 80° C.End temperature: 150° C.

Increments: 10° C.

specimen is sealed A to A at each sealbar temperature and seal strength(force) is determined at each step.

The temperature is determined at which the seal strength reaches 3 N.

Hot Tack Force:

The hot tack force is determined on a J&B Hot Tack Tester with anextrusion cast film of 100 μm thickness with the following furtherparameters:

Specimen width: 25.4 mm

Seal Pressure: 0.3 N/mm² Seal Time: 0.5 sec

Cool time: 99 secPeel Speed: 200 mm/secStart temperature: 90° C.End temperature: 140° C.

Increments: 10° C.

The maximum hot tack force, i.e the maximum of a force/temperaturediagram is determined and reported.

Haze and Clarity were determined according to ASTM D1003 on an extrusioncast film of 100 μm thickness.

B. Examples

The propylene copolymer (C-PP) has been produced in a Borstar PP pilotplant in a two-step polymerization process starting in a bulk-phase loopreactor followed by polymerization in a gas phase reactor, varying themolecular weight as well as hexene content by appropriate hydrogen andcomonomer feeds. The catalyst used in the polymerization process for(C-PP) was a metallocene catalyst as described in example 1 of EP 1 741725 A1. The catalyst used for the propylene homopolymer (H-PP1) and(H-PP2) is the commercial BCF20P catalyst (1.9 wt.-%Ti-Ziegler-Natta-catalyst as described in EP 0 591 224) of Borealis.

TABLE 1 Preparation of the components C-PP H-PP1 H-PP2 H-PP3 H-PP4 LoopMFR₂ [g/10 min] 1.0 8.6 0.9 Mw [kg/mol] 620 — — C6 [wt.-%] 0 0 0 XCS[wt.-%] 0.8 — — <2, 1> [mol-%] 0.6 GPR MFR₂ [g/10 min] 32 16 4.5 C6[wt.-%] 7.6 0 0 XCS [wt.-%] 4.5 — — Split Loop/ [%] 38/62 42/58 54/46GPR FINAL C6 [wt.-%] 4.7 0 0 0 0 XCS [wt.-%] 3.1 0.6 0.8 0.9 1.1 MFR₂[g/10 min] 8.1 3 12 12 2.8 Mw [kg/mol] 206 — — — — MWD [—] 3.0 — — — —Tm [° C.] 148 164 164 151 151.5 Tc [° C.] 100 110 115 105 107 <2, 1>[mol-%] — 0.0 0.0 0.9 0.9 Loop defines the propylene Copolymer fraction(A) GPR defines the propylene copolymer fraction (B); MFR₂, C6 and XCSare calculated from Loop and Final Final defines the propylene copolymer(C-PP) C6 is 1-hexene content <2, 1> are the <2, 1> regiodefects H-PP1is the commerical polypropylene homopolymer HC600TF of Borealis AGhaving an MFR₂ of 2.8 g/10 min. H-PP2 is the commerical polypropylenehomopolymer HE125MO of Borealis AG having an MFR₂ of 12 g/10 min.

TABLE 2 Properties of compounds CE 1 IE 1 IE 2 IE 3 IE 4 C-PP [wt.-%]100 85 85 85 85 H-PP1 [wt.-%] 0 15 0 0 0 H-PP2 [wt.-%] 0 0 15 0 0 H-PP3[wt.-%] 0 0 0 15 0 H-PP4 [wt.-%] 0 0 0 0 15 MFR [g/10 min] 7.8 7.2 9.08.7 6.8 Tm [° C.] 148 154 155 150 149 Tc [° C.] 100 106 107 105 103 SIT[° C.] 104 108 110 110 109 Sealing [° C.] 22 10 21 18 18 Range Haze [%]9.8 2.9 3.3 3.0 3.1 Clarity [%] 70.4 91 90 90 90

1. Polypropylene composition comprising (a) a propylene homopolymer(H-PP) having a melt flow rate MFR₂ (230° C.) measured according to ISO1133 in the range of 1.0 to 20.0 g/10 min, and (b) a propylene copolymer(C-PP) comprising (b-1) a polypropylene fraction (A) having a comonomercontent of not more than 1.0 wt.%, the comomers are C₅ to C₁₂ α-olefins,and (b-2) a propylene copolymer fraction (B) having a comonomer content4.0 to 20.0 wt.%, the comomers are C₅ to C₁₂ α-olefins, wherein further(c) the propylene copolymer (C-PP) has a comonomer content of at least2.0 wt.%, the comomers are C₅ to C₁₂ α-olefins, (d) the melt flow rateMFR₂ (230° C.) measured according to ISO 1133 of the propylenehomopolymer (H-PP) is higher than the melt flow rate MFR₂ (230° C.)measured according to ISO 1133 of the polypropylene fraction (A), (e)the weight ratio [(A)/(B)] of the polypropylene fraction (A) to thepropylene copolymer fraction (B) is in the range of 30/70 to 70/30, and(f) the weight ratio [(C-PP)/(H-PP)] of the propylene copolymer (C—PP)to the propylene homopolymer(H-PP) is in the range of 95/5 to 75/25. 2.Polypropylene composition according to claim 1, wherein the propylenehomopolymer (H-PP) has <2,1> regiodefects of less than 0.4 mol.%determined by ¹³C-spectroscopy.
 3. Polypropylene composition comprising:(a) a propylene homopolymer (H-PP) having <2,1> regiodefects of lessthan 0.4 mol.% determined by ¹³C-spectroscopy, and (b) a propylenecopolymer (C-PP) comprising (b-1) a polypropylene fraction (A) having acomonomer content of not more than 1.0 wt.%, the comomers are C₅ to C₁₂α-olefins, and (b-2) a propylene copolymer fraction (B) having acomonomer content 4.0 to 20.0 wt.%, the comomers are C₅ to C₁₂α-olefins, wherein further (c) the propylene copolymer (C-PP) has acomonomer content of at least 2.0 wt.%, the comomers are C₅ to C₁₂α-olefins, (d) the weight ratio [(A)/(B)] of the polypropylene fraction(A) to the propylene copolymer fraction (B) is in the range of 30/70 to70/30, and (e) the weight ratio [(C-PP)/(H-PP)] of the propylenecopolymer (C—PP) to the propylene homopolymer(H-PP) is in the range of95/5 to 75/25.
 4. Polypropylene composition according to claim 3,wherein: (a) the propylene homopolymer (H-PP) has a melt flow rate MFR₂(230° C.) measured according to ISO 1133 in the range of 1.0 to 20.0g/10 min, and/or (b) the melt flow rate MFR₂ (230° C.) measuredaccording to ISO 1133 of the propylene homopolymer (H-PP) is higher thanthe melt flow rate MFR₂ (230° C.) measured according to ISO 1133 of thepolypropylene fraction (A).
 5. Polypropylene composition according toclaim 1, wherein the polypropylene composition fulfills the equation(I):Tm−SIT≧24° C.  (I) wherein Tm is the melting temperature given incentigrade [° C.] of the polypropylene composition, SIT is the heatsealing initiation temperature (SIT) given in centigrade [° C.] of thepolypropylene composition.
 6. Polypropylene composition according toclaim 1, wherein the polypropylene composition has (a) a meltingtemperature Tm of at least 140° C., and/or (b) a temperature of equal ormore than 105° C. where 30% of the polypropylene composition is molten(30% of total enthalpy), and/or (c) a crystallization temperature Tc ofat least 100° C., and/or (d) a heat sealing initiation temperature (SIT)of not more than 120° C.
 7. Polypropylene composition according to claim1, wherein the polypropylene composition has: (a) a melt flow rate MFR₂(230° C.) measured according to ISO 1133 in the range of 1.0 to 50.0g/10 min, and/or (b) a comonomer content of 1.0 to 10.0 wt.%, and/or (c)a xylene soluble content (XCS) determined at 23° C. according to ISO6427 of below 18.0 wt.%.
 8. Polypropylene composition according to claim1, wherein the propylene homopolymer(H-PP) has: (a) melting temperatureTm of at least 140° C., and/or (b) a xylene soluble content (XCS)determined at 23° C. according to ISO 6427 of below 3.0 wt.-%. 9.Polypropylene composition according to claim 1, wherein the ratio MFR(A)/MFR(C-PP) of the propylene copolymer (C-PP) is below 1.0, wherein:MFR (A) is the melt flow rate MFR₂ (230° C.) [g/10 min] measuredaccording to ISO 1133 of the polypropylene fraction (A), MFR(C-PP) isthe melt flow rate MFR₂ (230° C.) [g/10 min] measured according to ISO1133 of the propylene copolymer (C-PP).
 10. Polypropylene compositionaccording to claim 1, wherein the propylene copolymer (C-PP) has: (a) amelt flow rate MFR₂ (230° C.) measured according to ISO 1133 in therange of 2.0 to 50.0 g/10 min, and/or (b) a melting temperature Tm of atleast 140° C., and/or (c) a xylene soluble content (XCS) determined at23° C. according to ISO 6427 of below 3.5 wt.%
 11. Polypropylenecomposition according to claim 1, wherein: (a) the propylene copolymer(C-PP) comprises (a1) at least 20.0 wt % of a crystalline fractionhaving a lamella thickness of at least 5.70 nm, and (a2) at least 10.0wt % of a crystalline fraction having a lamella thickness of below than3.0 nm, said crystalline fractions are determined by the stepwiseisothermal segregation technique (SIST), and/or (b) the comonomers ofthe propylene copolymer (C-PP) are selected from the group of C₅α-olefin, C₆ α-olefin, C₇ α-olefin, C₈ α-olefin, C₉ α-olefin, C₁₀α-olefin, C₁₁ α-olefin and C₁₂ α-olefin.
 12. Polypropylene compositionaccording to claim 1, wherein the polypropylene fraction (A) (a) has<2,1> regiodefects of equal or more than 0.4 mol.-% determined by¹³C-spectroscopy, and/or (b) is a propylene homopolymer, and/or (c) hasa melt flow rate MFR₂ (230° C.) measured according to ISO 1133 of notmore than 5.0 g/10 min, and/or (d) a xylene soluble content (XCS) ofbelow 2.0 wt.%.
 13. Polypropylene composition according to claim 1,wherein the propylene copolymer fraction (B) (a) comprises, preferablycomprises only, 1-hexene as comomer, and/or (b) has a melt flow rateMFR₂ (230° C.) measured according to ISO 1133 of more than 10.0 g/10min.
 14. The polypropylene composition of claim 1, being in the form ofa film.
 15. The polypropylene composition of claim 1, being provided ina coating of an extrusion coated substrate.
 16. Process for thepreparation of a polypropylene composition according to claim 1, whereinthe process comprises the steps of (A) a sequential polymerizationprocess comprising at least two reactors connected in series for thepreparation of the propylene copolymer (C-PP), wherein said sequentialpolymerization process comprises the steps of (A-1) polymerizing in afirst reactor (R-1) being a slurry reactor (SR), preferably a loopreactor (LR), propylene and optionally at least one C₅ to C₁₂ α-olefinobtaining a polypropylene fraction (A) as defined in as defined in claim1, (A-2) transferring said polypropylene fraction (A) and unreactedcomonomers of the first reactor in a second reactor (R-2) being a gasphase reactor (GPR-1), (A-3) feeding to said second reactor (R-2)propylene and at least one C₄ to C₁₀ α-olefin, (A-4) polymerizing insaid second reactor (R-2) and in the presence of said polypropylenefraction (A) propylene and at least one C₅ to C₁₂ α-olefin obtaining apropylene copolymer fraction (B) as defined in claim 1, saidpolypropylene fraction (A) and said propylene copolymer fraction (B)form the propylene copolymer (C-PP) as defined in claim 1, whereinfurther in the first reactor (R-1) and second reactor (R-2) thepolymerization takes place in the presence of a solid catalyst system(SCS), said solid catalyst system (SCS) comprises (i) a transition metalcompound of formula (I)R _(n)(Cp′)₂ MX ₂  (I) wherein “M” is zirconium (Zr) or hafnium (Hf),each “X” is independently a monovalent anionic σ-ligand, each “Cp′” is acyclopentadienyl-type organic ligand independently selected from thegroup consisting of substituted cyclopentadienyl, substituted indenyl,substituted tetrahydroindenyl, and substituted or unsubstitutedfluorenyl, said organic ligands coordinate to the transition metal (M),“R” is a bivalent bridging group linking said organic ligands (Cp′), “n”is 1 or 2, preferably 1, and (ii) optionally a cocatalyst (Co)comprising an element (E) of group 13 of the periodic table (IUPAC) and(B) blending said propylene copolymer (C-PP) obtained in step (A) with apropylene homopolymer (H-PP) as defined in claim 1, obtaining therebythe polypropylene composition as defined in claim
 1. 17. Processaccording to claim 16, wherein the transition metal compound of formula(I) is an organo-zirconium compound of formula (II):

wherein M is zirconium (Zr) or hafnium (Hf), X are ligands with a σ-bondto the metal “M”, R¹ are equal to or different from each other, and areselected from the group consisting of linear saturated C₁ to C₂₀ alkyl,linear unsaturated C₁ to C₂₀ alkyl, branched saturated C₁-C₂₀ alkyl,branched unsaturated C₁ to C₂₀ alkyl, C₃ to C₂₀ cycloalkyl, C₆ to C₂₀aryl, C₇ to C₂₀ alkylaryl, and C₇ to C₂₀ arylalkyl, optionallycontaining one or more heteroatoms of groups 14 to 16 of the PeriodicTable (IUPAC), R² to R⁶ are equal to or different from each other andare selected from the group consisting of hydrogen, linear saturatedC₁-C₂₀ alkyl, linear unsaturated C₁-C₂₀ alkyl, branched saturated C₁-C₂₀alkyl, branched unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀aryl, C₇-C₂₀ alkylaryl, and C₇-C₂₀ arylalkyl, optionally containing oneor more heteroatoms of groups 14 to 16 of the Periodic Table (IUPAC), R⁷and R⁸ are equal to or different from each other and selected from thegroup consisting of hydrogen, linear saturated C₁ to C₂₀ alkyl, linearunsaturated C₁ to C₂₀ alkyl, branched saturated C₁ to C₂₀ alkyl,branched unsaturated C₁ to C₂₀ alkyl, C₃ to C₂₀ cycloalkyl, C₆ to C₂₀aryl, C₇ to C₂₀ alkylaryl, C₇ to C₂₀ arylalkyl, optionally containingone or more heteroatoms of groups 14 to 16 of the Periodic Table(IUPAC), SiR¹⁰ ₃, GeR¹⁰ ₃, OR¹⁰, SR¹⁰ and NR¹⁰ ₂, wherein R¹⁰ isselected from the group consisting of linear saturated C₁-C₂₀ alkyl,linear unsaturated C₁ to C₂₀ alkyl, branched saturated C₁ to C₂₀ alkyl,branched unsaturated C₁ to C₂₀ alkyl, C₃ to C₂₀ cycloalkyl, C₆ to C₂₀aryl, C₇ to C₂₀ alkylaryl, and C₇ to C₂₀ arylalkyl, optionallycontaining one or more heteroatoms of groups 14 to 16 of the PeriodicTable (IUPAC), and/or R⁷ and R⁸ being optionally part of a C₄ to C₂₀carbon ring system together with the indenyl carbons to which they areattached, preferably a C₅ ring, optionally one carbon atom can besubstituted by a nitrogen, sulfur or oxygen atom, R⁹ are equal to ordifferent from each other and are selected from the group consisting ofhydrogen, linear saturated C₁ to C₂₀ alkyl, linear unsaturated C₁ to C₂₀alkyl, branched saturated C₁ to C₂₀ alkyl, branched unsaturated C₁ toC₂₀ alkyl, C₃ to C₂₀ cycloalkyl, C₆ to C₂₀ aryl, C₇ to C₂₀ alkylaryl, C₇to C₂₀ arylalkyl, OR¹⁰, and SR¹⁰, wherein R¹⁹ is defined as before, L isa bivalent group bridging the two indenyl ligands, preferably being aC₂R¹¹ ₄ unit or a SiR¹¹ ₂ or GeR¹¹ ₂, wherein, R¹¹ is selected from thegroup consisting of H, linear saturated C₁ to C₂₀ alkyl, linearunsaturated C₁ to C₂₀ alkyl, branched saturated C₁ to C₂₀ alkyl,branched unsaturated C₁ to C₂₀ alkyl, C₃ to C₂₀ cycloalkyl, C₆ to C₂₀aryl, C₇ to C₂₀ alkylaryl or C₇ to C₂₀ arylalkyl, optionally containingone or more heteroatoms of groups 14 to 16 of the Periodic Table(IUPAC).